1. Field of the Invention
The present invention relates to a mold for forming a screw, and more particularly to a mold for forming a screw with an auger tip.
2. Description of Related Art
Conventionally, there are two steps to form a screw with an auger tip; the first step is to use a threading device to form threads on a material, the other is to use a mold press to form the auger tip on the screw. The mold press has two symmetrical parts operatively aligned with each other. When the threads is formed on the periphery of the material, the material is transported to the mold press to continuously form the auger tip. The mold press, as stated earlier, has two symmetrical parts each one of which comprises a first mold (50) and a second mold (40) detachably received in the first mold (50). The first mold (50) has a U shape cutout (51) and a first screw hole (52) defined to communicate with the U shape cutout (51). The second mold (40) forms thereon a forming edge (41), a conical recess (42) defined in a side thereof and a stop (43) formed on a face corresponding to that of the forming edge (41). The second mold (40) is able to be snugly fitted into the U shape cutout (51), whereby a first screw (53) is able to be threadingly inserted through the screw hole (52) and into the conical recess (42) of the second mold (40) to securely position the second mold (40) with respect to the first mold (50). It is known that after the first mold (50) and the second mold (40) are assembled to become a half of the mold press, the user is able to use two halves of the assembled first and second molds (40,50) to form an auger tip on a screw. Because the forming of the auger tip on the screw needs a pair of assembled first and second molds (40,50) to oppositely collide with each other, so as that two forming edges (41) are able to form an auger tip of the screw. After continuous collision between two forming edges (41) to form the auger tip on the screw, damage to the forming edge (41) is inevitable, although the provision of the stop (43) is to prolong the life span of the mold press. Therefore, a replacement of the second mold (40) is required. Due to the concern of continuous collision between two assembled first and second molds (40,50), the second mold (40) is made of a material of high strength and hardness, such as tungsten-carbide. As well known in the art, the tungsten is quite expensive, thus the replacement of the second mold (40) will increase the cost and will also cause an environment problem. Furthermore, when forming an auger tip of different type on the screw, the user will have to replace the second mold (40) altogether, which will certainly increase the cost.
The present invention aims to provide an improved mold to form an auger tip on a screw so as to mitigate and/or obviate the aforementioned problems.